Monday, November 22, 2010

Large-scale fences for land management are socially and ecologically contentious. Inside the Southern Buffalo Fence in the Okavango there has been a dramatic reduction in standing vegetative biomass since its construction in 1982/3. Notably, the area that has exhibited most vegetation change – an apparent loss in tree cover and diversity and a reduction in standing plant biomass – is inside the protected wildlife management area, while the open access tribal grazing area appears little changed. Anecdotal evidence provided by wildlife veterinarians points to blocked migration routes for zebras, but the heavy presence inside the fence of elephants, along with visible tree damage, indicate that they might also be playing an important role. In her presentation, Dr Lin Cassidy presented preliminary findings from paired point samples of vegetation characteristics and from analysis of satellite derived landscape characteristics: amount of standing vegetation, surface temperature, surface moisture and soil brightness. The data shows that :• More thornveld on cattle side than on wildlife side (possibly due to ring-barking by elephants – • More woodland on cattle side, with more scrub on wildlife side• Greater areas of exposed soil on wildlife side, particularly in the growing (rainy) season• Clear evidence of reduction in standing vegetative biomass on wildlife side• Introduction of a sharp boundary into what was previously a gradient of changeResearch is ongoing, with next steps being the analysis of differences in grass diversity, woody species diversity and bird species diversity between the two sides.